Nonlinear FE analysis on stiffness and resistance of bolted cold-formed steel built-up joints

Abstract

This paper describes a computer-based finite element (FE) approach for investigating the stiffness and resistance behaviour of beam-column moment joints in the portal frame constructed by cold-formed steel (CFS) back-to-back channel sections. A total of 8 specimens constructed by flat sheets and bolt are tested in the study. The applicability of the numerical simulation approach is validated against the experimental outcomes. Based on the FE simulations, a modified equation is proposed to predict the initial flexibility of four-layer CFS lap joints under tension. Parametric studies consisting of 18 four-layer bolted connections and 27 beam-column bolted models are conducted based on the validated model to investigate the effects of sheet width-to-thickness ratio, bolt-to-bolt hole tolerance and overlap length on the flexibility of the connection and to reveal the influence of bolt spacing, gusset plate thickness and beam profile on the failure behaviours, moment transfer coefficients and ultimate resistance of CFS beam-column moment joints. The FE obtained results indicate that increasing bolt spacing is a better option to improve the joint capacity when compared with increasing gusset plate thickness. The flexural capacity of the CFS bolted built-up joints with varying sectional configurations can meet the criterion of the existing design specifications such as Eurocode and US code.